Using AEGP_IterateGeneric correctly

Question

I am attempting to use AEGP_IterateGeneric to parallelize my processing over all available cores. I'm having trouble handling PF_Interrupt_CANCEL correctly. This is what the end of my iteration callback looks like:
long progress = InterlockedIncrement(&pr->progress);
if(thread_indexL == 0)
   return PF_PROGRESS(pr->in_data, pr->progress, iterationsL);
else
   return PF_Err_NONE;
pr->progress is a shared progress value among all threads. it will reach the progress total when my iteration is done.
This appears to work, when my frame rendering gets really slow a progress bar appears below the output window.
Now, when the user is adjusting a parameter, the pixels that are processed by thread_indexL == 0 turn to garbage frequently (flickering between junk data and my processed pixels.) The rest of the pixels (processed by thread_indexL != 0) are OK.
What is the correct way to implement PF_PROGRESS in IterateGeneric that does not result in artifacts and maintains the expected responsiveness from my plugin?

Answer 1

which format of the image are you trying to threshold. If you want to threshold an RGB image (JPG for ex). Then you have to convert that into a grey scale image (Extract color planes). If you want to threshold a RGB image directly then use "Color thresholding"